The present invention relates generally to seat belt retractors and in particular to a flat seat belt retractor incorporated into a seat back frame which retracts a portion of the belt webbing into the seat back frame for storage of the belt webbing.
Seat belts for motor vehicles typically include a belt webbing that is attached at one end to the vehicle structure and at the other end to a webbing retractor attached to the vehicle structure. A clasp slidably mounted on the webbing is insertable into a buckle after pulling a portion of the webbing from the retractor, forming a lap belt and a shoulder belt for a seat occupant. Commonly used seat belt webbing retractors wind the webbing around a rotating spool to retract the webbing into the retractor housing. To store a sufficient quantity of belt webbing for large seat occupants, it is necessary that the retractor housing be relatively large.
To improve both the comfort and performance of seat belt restraint systems, seats are being developed which have the belt restraint system mounted to the seat rather than to the vehicle body. This improves the comfort and performance of the restraint system by maintaining the belt anchor points in fixed positions relative to the seat occupant, regardless of the adjusted position of the seat within the vehicle body.
When a seat belt restraint system is mounted to a seat as opposed to being mounted directly to the vehicle structure adjacent to the seat, it is necessary for the retractor to be "packaged" or contained within the interior of the seat. Due to the large space required for a spool type retractor, it is often difficult to package such a retractor within a seat, either the seat cushion or the seat back.
Accordingly, it is an object of the present invention to provide a seat belt webbing retractor of a reduced thickness compared to a spool type retractor to facilitate the packaging of the retractor within a seat.
It is a feature of the present invention to provide an elongated housing with an opening into which the webbing is retracted by moving the webbing through the length of the housing. By attaching the webbing to a slide movable along the length of the housing, the webbing will be retracted into the housing as the slide moves away from the housing opening or the webbing will be protracted from the housing as the slide moves toward the opening. As a result, the webbing remains generally flat within the housing, rather than being wound on a spool and thus, the retractor is of a reduced thickness compared to a spool type retractor and therefore easier to package within a seat assembly.
It is a further feature of the present invention to incorporate the retractor housing into a structural frame member of the seat back. This results in a dual function for the frame member, reducing the number of separate components required in the seat back frame and retractor. In a preferred embodiment, the seat back frame includes a diagonal frame member extending from one upper corner of the seat back frame to an opposite lower corner with the seat belt webbing retractor being contained within the diagonal frame member. An opening at the upper corner of the seat back frame is used for the webbing to pass into and out of the seat back frame.
The retractor preferably includes an inertia latch mechanism to prevent protraction of the belt webbing in the event of a vehicle acceleration beyond a predetermined level. An inertia latch is provided by a locking pawl having a lever rotatable into engagement with the teeth of a gear rack along the path of travel of the retractor slide. When an acceleration of a predetermined value is experienced, the latch pawl will rotate to engage the lever with the teeth of the stationary rack, thus locking the slide in place and preventing movement of the slide toward the opening through which the belt webbing is protracted.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.